1. Field of the Invention
The instant disclosure relates to a method, a method, and an apparatus with environmental noise cancellation, in particular, a real-time noise suppression procedure is introduced to the system or the related apparatus with a microphone array for providing an improved voice quality.
2. Description of Related Art
For acquiring a solution regarding distress caused by environmental noise during a call procedure, an aspect of dual-microphone array has been developed for suppressing the noise. The related noise cancellation scheme particularly introduces a primary microphone for receiving the voice and the nearby noise, and a secondary microphone installed with a distance from the primary one for receiving the sound with majority of environmental noise. The signals received by the two microphones can be used to effectively suppress the noise in order to improve the call quality.
Reference is made to FIG. 1 depicting a communication device having two microphones in a conventional scheme. Such as an example illustrated in U.S. Pat. No. 6,549,586, the communication device has two microphones such as a first microphone 101 distanced at a distance from a user's mouth and a second microphone 102 installed near the mouth. Main function of the first microphone 101 is to collect the background noise since it has the distance from the mouth, however the first microphone 101 may also receive the speech. The second microphone 102 is mainly collecting the voice. The difference between the two microphones serves as the function of noise suppression.
In the current example, in order to suppress the background noise collected by the first microphone 101, the signals are firstly buffered in a first memory 103. A first subtractor 105 is functioned to enhance the estimation of background noise. Further, the main signals of voice and background noise collected by the second microphone 102 are buffered in the second memory 104. The second subtractor 106 refers to the background noise estimated by the first subtractor 105 through the delay circuit 107. The subtractor 106 therefore enhances the suppression of the background noise collected by the second microphone 102.
Further in the example, the shown third subtractor 108 then simultaneously receives the estimated background noise collected by the first subtractor 105 and the speech estimated by the second subtractor 106. After that, subtractor 108 obtains the speech signals after noise suppression through parameters adjustment. The signals are output to an inverse fast Fourier transform (IFFT) 109 which transforms the signal at discrete time to the continuous signals at frequency domain. An overlap-and-add unit 110 then combines the signals and produces speech signals.
Based on the aspect of the microphone array described in FIG. 1, U.S. Pat. No. 7,587,056 owned by Fortemedia™ for the purpose shows an array microphone apparatus and a noise suppression method thereof. Some further processes, including signal calibration, beamforming, noise estimation, and suppression, and time-frequency domain transformation, were provided to obtain improved call quality.
Some disadvantages of the conventional arts are obviously shown. For example, the quality requirements of microphones are high since the conventional technology lacks effective calibration. Further, a high gain matching scheme is required to the microphone since fixed-type beamforming circuit is used to extract the speech. Still, a lot of noises are mixed up with the speech by the fixed-type beamforming, so the noise suppression may be affected, and the speech may be distorted if any noise-suppression is performed thereon.